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Improved geometry calculation for all disk images, not just those listed in DiskAPI.js

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Jeff Parsons 2017-06-01 20:59:41 -07:00 • committed by Jeff Parsons
commit 5441c6346b
5 changed files with 76 additions and 61 deletions
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73
modules/shared/lib/diskapi.js
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@ -68,48 +68,12 @@ var DiskAPI = {
}
};
/*
* Common (supported) diskette formats
*
* For no particular reason that I can recall, each entry in DISK_FORMATS is an array of values in "CHS" order:
*
* [# cylinders, # heads, # sectors/track, # bytes/sector, media type]
*
* If the 4th value is omitted, the sector size is assumed to be 512. The order of these "geometric" values mirrors
* the structure of our JSON-encoded disk images, which consist of an array of cylinders, each of which is an array of
* heads, each of which is an array of sector objects.
*/
DiskAPI.DISK_FORMATS = {
163840: [40,1,8,,0xFE], // media type 0xFE: 40 cylinders, 1 head (single-sided), 8 sectors/track, ( 320 total sectors x 512 bytes/sector == 163840)
184320: [40,1,9,,0xFC], // media type 0xFC: 40 cylinders, 1 head (single-sided), 9 sectors/track, ( 360 total sectors x 512 bytes/sector == 184320)
327680: [40,2,8,,0xFF], // media type 0xFF: 40 cylinders, 2 heads (double-sided), 8 sectors/track, ( 640 total sectors x 512 bytes/sector == 327680)
368640: [40,2,9,,0xFD], // media type 0xFD: 40 cylinders, 2 heads (double-sided), 9 sectors/track, ( 720 total sectors x 512 bytes/sector == 368640)
737280: [80,2,9,,0xF9], // media type 0xF9: 80 cylinders, 2 heads (double-sided), 9 sectors/track, (1440 total sectors x 512 bytes/sector == 737280)
1228800: [80,2,15,,0xF9], // media type 0xF9: 80 cylinders, 2 heads (double-sided), 15 sectors/track, (2400 total sectors x 512 bytes/sector == 1228800)
1474560: [80,2,18,,0xF0], // media type 0xF0: 80 cylinders, 2 heads (double-sided), 18 sectors/track, (2880 total sectors x 512 bytes/sector == 1474560)
2949120: [80,2,36,,0xF0], // media type 0xF0: 80 cylinders, 2 heads (double-sided), 36 sectors/track, (5760 total sectors x 512 bytes/sector == 2949120)
/*
* The following are some common partition sizes, which we explicitly map to CHS values, since MBR/BPB values
* can mislead us when attempting to determine the exact disk geometry. TODO: Investigate. Is it possible that
* usable space on early hard disks was reduced to reserve the last cylinder for diagnostics, head parking, etc?
*/
10618368:[306,4,17], // PC XT 10Mb hard drive (type 3)
21368320:[615,4,17], // PC AT 20Mb hard drive (type 2)
/*
* Assorted DEC disk formats.
*/
256256: [77, 1,26,128], // RX01 single-platter diskette: 77 tracks, 1 head, 26 sectors/track, 128 bytes/sector, for a total of 256256 bytes
2494464: [203,2,12,512], // RK03 single-platter disk cartridge: 203 tracks, 2 heads, 12 sectors/track, 512 bytes/sector, for a total of 2494464 bytes
5242880: [256,2,40,256], // RL01K single-platter disk cartridge: 256 tracks, 2 heads, 40 sectors/track, 256 bytes/sector, for a total of 5242880 bytes
10485760:[512,2,40,256] // RL02K single-platter disk cartridge: 512 tracks, 2 heads, 40 sectors/track, 256 bytes/sector, for a total of 10485760 bytes
};
/*
* TODO: Eventually, our tools will need to support looking up disk formats by "model" rather than by raw disk size,
* because obviously multiple disk geometries can yield the same raw disk size. For each conflict that arises, I'll
* probably create a fake (approximate) disk size entry above, and then create a mapping to that approximate size below.
*/
DiskAPI.DISK_MODELS = {
DiskAPI.MODELS = {
"RL01": 5242880,
"RL02": 10485760
};
@ -177,6 +141,41 @@ DiskAPI.BPB = {
LARGE_SECS: 0x020 // 4 bytes (DOS 3.31 and up): number of sectors if TOTAL_SECS is zero
};
/*
* Common (supported) diskette geometries.
*
* Each entry in GEOMETRIES is an array of values in "CHS" order:
*
* [# cylinders, # heads, # sectors/track, # bytes/sector, media type]
*
* If the 4th value is omitted, the sector size is assumed to be 512. The order of these "geometric" values mirrors
* the structure of our JSON-encoded disk images, which consist of an array of cylinders, each of which is an array of
* heads, each of which is an array of sector objects.
*/
DiskAPI.GEOMETRIES = {
163840: [40,1,8,,0xFE], // media type 0xFE: 40 cylinders, 1 head (single-sided), 8 sectors/track, ( 320 total sectors x 512 bytes/sector == 163840)
184320: [40,1,9,,0xFC], // media type 0xFC: 40 cylinders, 1 head (single-sided), 9 sectors/track, ( 360 total sectors x 512 bytes/sector == 184320)
327680: [40,2,8,,0xFF], // media type 0xFF: 40 cylinders, 2 heads (double-sided), 8 sectors/track, ( 640 total sectors x 512 bytes/sector == 327680)
368640: [40,2,9,,0xFD], // media type 0xFD: 40 cylinders, 2 heads (double-sided), 9 sectors/track, ( 720 total sectors x 512 bytes/sector == 368640)
737280: [80,2,9,,0xF9], // media type 0xF9: 80 cylinders, 2 heads (double-sided), 9 sectors/track, (1440 total sectors x 512 bytes/sector == 737280)
1228800: [80,2,15,,0xF9], // media type 0xF9: 80 cylinders, 2 heads (double-sided), 15 sectors/track, (2400 total sectors x 512 bytes/sector == 1228800)
1474560: [80,2,18,,0xF0], // media type 0xF0: 80 cylinders, 2 heads (double-sided), 18 sectors/track, (2880 total sectors x 512 bytes/sector == 1474560)
2949120: [80,2,36,,0xF0], // media type 0xF0: 80 cylinders, 2 heads (double-sided), 36 sectors/track, (5760 total sectors x 512 bytes/sector == 2949120)
/*
* The following are some common disk sizes and their CHS values, since missing or bogus MBR and/or BPB values
* might mislead us when attempting to determine the exact disk geometry.
*/
10653696:[306,4,17], // PC XT 10Mb hard drive (type 3)
21411840:[615,4,17], // PC AT 20Mb hard drive (type 2)
/*
* Assorted DEC disk formats.
*/
256256: [77, 1,26,128], // RX01 single-platter diskette: 77 tracks, 1 head, 26 sectors/track, 128 bytes/sector, for a total of 256256 bytes
2494464: [203,2,12,512], // RK03 single-platter disk cartridge: 203 tracks, 2 heads, 12 sectors/track, 512 bytes/sector, for a total of 2494464 bytes
5242880: [256,2,40,256], // RL01K single-platter disk cartridge: 256 tracks, 2 heads, 40 sectors/track, 256 bytes/sector, for a total of 5242880 bytes
10485760:[512,2,40,256] // RL02K single-platter disk cartridge: 512 tracks, 2 heads, 40 sectors/track, 256 bytes/sector, for a total of 10485760 bytes
};
/*
* Media descriptor bytes for DOS-compatible FAT-formatted disks (stored in the first byte of the FAT)
*/